Touch controller and pen

Abstract

[Problem] To suppress the occurrence of erroneous detection of an uplink signal due to noise, while ensuring backward compatibility. [Solution] This touch controller transmits an uplink signal US having a structure in which a data portion is disposed behind a preamble portion, wherein the preamble portion includes a preamble PRE1 corresponding to a first protocol and a preamble PRE2 corresponding to a second protocol different from the first protocol, the data portion has a format common to the first protocol and the second protocol, and the preamble PRE2 is disposed before the preamble PRE1.

Description

Touch Controller and Pen

[0001] The present invention relates to a touch controller and a pen, and particularly relates to a touch controller and a pen that perform two-way communication by an active electrostatic method.

[0002] A pen compatible with the active electrostatic method (hereinafter simply referred to as "pen") is configured to receive an uplink signal transmitted from the touch controller through a touch sensor, determine a transmission / reception schedule based on the reception timing, and transmit a downlink signal and receive a next uplink signal in accordance with the determined transmission / reception schedule.

[0003] The uplink signal includes a preamble portion including a known autocorrelation code, and a data portion including data transmitted by the touch controller to the pen. While the pen is performing the reception operation of the uplink signal, it continuously calculates the correlation value between the signal received by the nib electrode provided at the pen nib and the known autocorrelation code, and detects the timing at which the calculated correlation value exceeds a predetermined value, thereby detecting the preamble portion and the uplink signal including the preamble portion. Patent Document 1 discloses an example of a pen that performs the above-described uplink signal reception operation.

[0004] International Publication No. WO 2017 / 029836

[0005] However, external noise may be superimposed on the signal received by the pen. Depending on the magnitude and characteristics of this noise, the pen may falsely detect the preamble portion, which will cause the pen to determine an incorrect transmission / reception schedule. As a result, the transmission and reception of the downlink signal and the uplink signal cannot be performed normally, and fatal malfunctions such as broken lines during drawing occur.

[0006] As one method for solving such a problem, it is conceivable to substantially improve the signal-to-noise ratio (SNR) by making the preamble portion longer than before. However, changing the configuration of the preamble portion results in loss of backward compatibility with older pens.

[0007] Therefore, one of the objectives of the present invention is to provide a touch controller and pen that suppress the occurrence of false uplink signal detection due to noise while ensuring backward compatibility.

[0008] The touch controller according to the present invention is a touch controller that transmits an uplink signal having a structure in which a data section is arranged after a preamble section, wherein the preamble section includes a first preamble corresponding to a first protocol and a second preamble corresponding to a second protocol different from the first protocol, the data section has a format common to the first protocol and the second protocol, and the second preamble is arranged before the first preamble.

[0009] The pen according to the present invention is a pen that receives an uplink signal having a structure in which a data section is arranged behind a preamble section, and receives the preamble section by detecting that a second preamble corresponding to a second protocol and a first preamble corresponding to a first protocol different from the second protocol are arranged in this order, determines a transmission and reception schedule based on the reception timing of the preamble section, and receives the data section and the preamble section of the next uplink signal according to the determined transmission and reception schedule.

[0010] According to the present invention, it is possible to provide an uplink signal that can be received by older pens that do not support the second protocol, while having a longer preamble section compared to conventional uplink signals that have only a first preamble. This makes it possible to suppress the occurrence of false detection of uplink signals due to noise while ensuring backward compatibility.

[0011] (a) is a diagram showing the configuration of a position detection system 1 according to an embodiment of the present invention, and (b) is a diagram showing the configuration of a plurality of sensor electrodes constituting the touch sensor 30 shown in (a). This is a diagram showing the configuration of the uplink signal US. (a) and (b) are diagrams showing specific examples of preambles PRE1 and PRE2, respectively. This is a diagram showing the processing performed by the processing circuit 20 of the pen 2 to receive the uplink signal US and transmit the downlink signal DS. This is a diagram showing the processing performed by the processing circuit 20 of the pen 2 to receive the uplink signal US and transmit the downlink signal DS. (a) to (d) are diagrams showing the configuration of the uplink signal US according to the first to fourth modifications of the embodiment of the present invention, respectively. (a) and (b) are diagrams showing the configuration of the uplink signal US used in the fifth modification of the embodiment of the present invention. (a) and (b) are diagrams showing methods for simultaneously transmitting two types of uplink signals US1 and US2, respectively.

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0013] Figure 1(a) shows the configuration of a position detection system 1 according to an embodiment of the present invention. As shown in the figure, the position detection system 1 is configured to include a pen 2 and a position detection device 3.

[0014] The position detection device 3 is a computer that responds to pen input to a flat surface, which is a touch surface 3a, and as shown in Figure 1(a), it is configured to include a touch sensor 30, a touch controller 31, and a host processor 32. The position detection device 3 may be an electronic device such as a tablet terminal where the touch surface also serves as the display surface, or it may be a digitizer where the touch surface does not serve as the display surface.

[0015] The touch sensor 30 is a sensor used by the touch controller 31 to perform bidirectional communication with the pen 2, and is configured to have multiple sensor electrodes.

[0016] Figure 1(b) shows the configuration of the multiple sensor electrodes that make up the touch sensor 30. As shown in the figure, the multiple sensor electrodes that make up the touch sensor 30 include multiple X electrodes 30X arranged at equal intervals along the X direction (direction within the touch surface 3a) and each extending in the Y direction (direction perpendicular to the X direction within the touch surface 3a), and multiple Y electrodes 30Y arranged at equal intervals along the Y direction and each extending in the X direction. Each X electrode 30X and each Y electrode 30Y are individually connected to the touch controller 31.

[0017] The touch controller 31 is an integrated circuit that performs bidirectional communication with the pen 2 via the touch sensor 30. Through this bidirectional communication, the touch controller 31 is configured to detect the position of the pen 2 within the touch surface 3a, acquire data transmitted by the pen 2, and sequentially supply these to the host processor 32. The touch controller 31 may also be configured to detect the position of a passive pointer, such as a finger, within the touch surface 3a via the touch sensor 30, and in that case, the touch controller 31 is configured to sequentially supply the detected position of the passive pointer to the host processor 32 as well.

[0018] The specific method of bidirectional communication between the pen 2 and the touch controller 31 is not particularly limited, but the following explanation will continue assuming the use of an active electrostatic method. In the following, the signal transmitted from the touch controller 31 to the pen 2 will be referred to as the uplink signal US, and the signal transmitted from the pen 2 to the touch controller 31 will be referred to as the downlink signal DS. The uplink signal US includes commands indicating the control content for the pen 2. The details of the configuration of the uplink signal US will be explained separately later. The downlink signal DS includes a position signal, which is an unmodulated carrier signal, and a data signal, which is a carrier signal modulated by predetermined data.

[0019] The host processor 32 is the central processing unit of the position detection device 3 and plays the role of executing the operating system and various applications of the position detection device 3 by reading and executing programs stored in a memory (not shown). The various applications executed by the host processor 32 may include drawing applications. This drawing application is configured to have, for example, a function to generate stroke data based on data supplied from the touch controller 31 (position of pen 2 or passive pointer, and data transmitted by pen 2), a function to generate digital ink based on the generated stroke data, and a function to render the generated digital ink and display it on a display.

[0020] As shown in Figure 1(a), the pen 2 is composed of a processing circuit 20, a battery 21, a core body 22, a pen tip electrode 23, and a pressure sensor 24. The processing circuit 20 is a processor that performs the various processes of the pen 2 described later by reading and executing a program stored in a memory (not shown), and is configured to operate using power supplied from the battery 21. The core body 22 is a component that constitutes the pen tip of the pen 2. The pen tip electrode 23 is a conductor placed near the tip of the core body 22 and is electrically connected to the processing circuit 20. The pressure sensor 24 is a sensor that detects a writing pressure value indicating the pressure applied to the pen tip of the pen 2, and is connected to the rear end of the core body 22. The writing pressure value detected by the pressure sensor 24 is supplied to the processing circuit 20.

[0021] The processing circuit 20 receives the uplink signal US via the pen tip electrode 23 and performs processing to determine the transmission and reception schedule for the downlink signal DS and the uplink signal US based on the reception timing and the information in the uplink signal US. The processing circuit 20 also generates the downlink signal DS in response to the control of the command in the uplink signal US and transmits it via the pen tip electrode 23 according to the determined transmission and reception schedule. Details of these processes will be described later. The data signals constituting the downlink signal DS may include the pen pressure value detected by the pressure sensor 24 and the pen ID pre-stored in the processing circuit 20's built-in memory.

[0022] The processing circuit 20 incorporates multiple correlators, each having the function of calculating a correlation value between an input code sequence and a pre-set code sequence. These correlators are used to detect the uplink signal US. Further details will be described later.

[0023] Figure 2 shows the configuration of the uplink signal US. As shown in the figure, the uplink signal US is composed of a preamble section and a data section, of which the data section is composed of data DATA including the command described above.

[0024] The preamble section consists of two preambles PRE1 and one preamble PRE2. Preamble PRE1 is a preamble included in the uplink signal US according to the background technology of the present invention, and corresponds to an older type of protocol (hereinafter referred to as the "old protocol") from the perspective of the present invention. On the other hand, preamble PRE2 is a preamble not included in the uplink signal US according to the background technology of the present invention, and corresponds to a new type of protocol (hereinafter referred to as the "new protocol") from the perspective of the background technology of the present invention.

[0025] As shown in Figure 2, the two preambles PRE1 are arranged side by side in front of the data section, and the preamble PRE2 is arranged in front of the two preambles PRE1. The data section has a format common to both the old and new protocols. The structure in which the two preambles PRE1 and the data section are arranged in this order is the same as the structure of the uplink signal US in the background art of the present invention. Therefore, a pen in the background art of the present invention that cannot detect the preamble PRE2 can detect the uplink signal US by detecting the portion of the uplink signal US consisting of the two preambles PRE1 and the data section, so it can be said that the uplink signal US in this embodiment is backward compatible.

[0026] On the other hand, the pen 2 according to this embodiment, which can detect the preamble PRE2, will detect the entire uplink signal US shown in Figure 2 as the uplink signal US. Therefore, the uplink signal US detected by the pen 2 in this embodiment has a longer preamble portion than the uplink signal US according to the background art of the present invention. Thus, it can be said that the uplink signal US according to this embodiment makes it possible to suppress the occurrence of false detection of the uplink signal US due to noise.

[0027] Preferably, preamble PRE2 is configured to have a time-symmetric configuration with respect to preamble PRE1. In other words, preamble PRE2 is preferably configured with a second code sequence obtained by time-reversing the first code sequence that constitutes preamble PRE1. This point will be explained in detail below with reference to the specific example shown in Figure 3.

[0028] Figures 3(a) and 3(b) show specific examples of preambles PRE1 and PRE2, respectively. As shown in these figures, preambles PRE1 and PRE2 are each composed of a 40-chip length code sequence (autocorrelation code) having good autocorrelation characteristics. This code sequence constitutes a spreading code using a direct sequence spread spectrum (DSSS) method, and the touch controller 31 is configured to transmit preambles PRE1 and PRE2 by transmitting this 40-chip length code sequence using, for example, BPSK (binary phase shift modulation).

[0029] Figure 3(a) also shows the structure of the 40-chip code sequence. As shown in the figure, the 40-chip code sequence that makes up the preamble PRE1 is obtained by converting five words, each being a hexadecimal number (0 to F), into a chip sequence consisting of four chips, each being either 0 or 1, and then performing Manchester coding on this chip sequence. Manchester coding is an encoding method that encodes chip "0" to "10" and chip "1" to "10", so that three or more identical values ​​do not occur consecutively. Therefore, the preamble PRE1 is configured so that three or more identical values ​​do not occur consecutively.

[0030] Figure 3(a) shows a specific example of a code sequence with a length of 40 chips. However, any code sequence that does not have three or more consecutive identical values ​​and has good autocorrelation characteristics can be suitably used as preambles PRE1 and PRE2. When a code sequence obtained by reversing the time of preamble PRE1 is used as preamble PRE2, if there are no three or more consecutive identical values ​​in preamble PRE1, there will be no three or more consecutive identical values ​​in preamble PRE2 either, and the autocorrelation characteristics of preamble PRE2 will be the same as those of preamble PRE1.

[0031] Figures 4 and 5 show the processes executed by the processing circuit 20 of the pen 2 to receive the uplink signal US and transmit the downlink signal DS. The processes executed by the processing circuit 20 of the pen 2 using the uplink signal US, as explained with reference to Figures 2 and 3, will be described in detail below, with reference to these figures.

[0032] The processing circuit 20 first waits to resume processing until the timing to start receiving the uplink signal US arrives (step S1). If pairing, as described later, has been established, this timing will follow the predetermined transmission and reception schedule. On the other hand, if pairing, as described later, has not been established, the processing circuit 20 will continuously or intermittently perform the receiving operation of the uplink signal US.

[0033] In step S1, the processing circuit 20, having determined that the timing has arrived, uses the multiple correlators described above to calculate the correlation value between the signal received via the pen tip electrode 23 (the code sequence obtained by demodulation) and each code sequence constituting the preamble section shown in Figure 2 (specifically, the 40-chip length code sequence constituting preamble PRE1 and the 40-chip length code sequence constituting preamble PRE2) (step S2). The processing circuit 20 performs this calculation for each chip length of the code sequence, and if the calculated correlation value exceeds a predetermined value, it determines that the preamble corresponding to the code sequence used to calculate the correlation value has been detected.

[0034] Each time the calculation in step S2 is performed, the processing circuit 20 determines whether or not it has detected a structure that looks like a preamble section, that is, a structure in which preamble PRE2, preamble PRE1, and preamble PRE1 are arranged in that order (step S3). If it is determined that it has been detected, the process moves to step S8. On the other hand, if it is determined that it has not been detected, it determines whether or not a predetermined time has elapsed since the start of the uplink signal US reception operation (i.e., whether or not a timeout has occurred). If it is determined that the time has not elapsed, it returns to step S2 and re-executes the calculation of the correlation value. If it is determined that the time has elapsed, the process moves to step S5.

[0035] In step S5, the processing circuit 20 determines whether a predetermined time has elapsed since the last reception of the uplink signal US (i.e., since the last affirmative determination in step S9, described later). If it determines that the time has elapsed, it determines whether or not pairing with the touch controller 31 is in progress (step S6). If pairing is in progress, it cancels the pairing by deleting the stored local ID in step S13, described later (step S7), and then returns to step S1 to wait for the next reception operation start timing. If it determines in step S5 that the predetermined time has not elapsed, or if it determines in step S6 that pairing is not in progress, the processing circuit 20 returns to step S1 without performing step S7 and waits for the next reception operation start timing.

[0036] In step S8, the processing circuit 20 checks the time symmetry between the detected preamble PRE2 (or the part that looks like it) and the first preamble PRE1 (or the part that looks like it) (step S8), and determines whether or not there is time symmetry between them (step S9). Specifically, the processing circuit 20 checks whether the part that looks like preamble PRE2 is a code sequence that is the time inverted version of the part that looks like preamble PRE1. If it is determined that it is a time inverted code sequence, it determines that there is time symmetry, and if it is determined that it is not a time inverted code sequence, it determines that there is no time symmetry.

[0037] If the processing circuit 20 determines in step S9 that there is no time symmetry, it moves on to step S5. In this case, the processing circuit 20 determines that the structure detected in step S3 is not the preamble section, and therefore the uplink signal US was not detected. On the other hand, if the processing circuit 20 determines in step S9 that there is time symmetry, it moves on to step S10 in Figure 5, and determines the transmission and reception schedule for the downlink signal DS and the uplink signal US based on the reception timing of the preamble section (step S10). The transmission and reception schedule thus determined repeats the transmission of the downlink signal DS and the reception of the uplink signal US at predetermined intervals. Depending on the protocol that defines the bidirectional communication between the pen 2 and the touch controller 31, one cycle may be divided into multiple time slots, and in that case, the transmission and reception schedule includes information that identifies one or more time slots to be used for transmitting the downlink signal DS.

[0038] In step S10, the processing circuit 20, having determined the transmission and reception schedule, receives the data section following the preamble section and demodulates it to obtain the command transmitted by the touch controller 31 (step S11). The processing circuit 20 then determines whether or not it is currently paired with the touch controller 31 (step S12). If it is not currently paired, it establishes pairing with the touch controller 31 by storing the local ID included in the command obtained in step S11 (step S13).

[0039] Here, the data portion of the uplink signal US contains information about a local ID to be assigned to an unpaired pen 2, and the local ID that the processing circuit 20 stores in step S13 is the local ID indicated by this information. Furthermore, when the touch controller 31 sends a command to a specific pen 2, it places the local ID assigned to that pen 2 within the command. This allows the pen 2 to determine whether or not it needs to process the command by referring to the local ID within the command.

[0040] Next, the processing circuit 20 generates a downlink signal DS (step S14). As described above, this downlink signal DS includes a position signal and a data signal. The data used for modulating the data signal includes the pen pressure value detected by the pressure sensor 24 shown in Figure 1(a), and data corresponding to the commands acquired in step S11 that the processing circuit 20 determines require processing (such as the pen ID described above).

[0041] Next, the processing circuit 20 determines whether the transmission timing for the downlink signal DS has arrived based on the transmission / reception schedule determined in step S10 (step S15). If it determines that the timing has arrived, it transmits at least a portion of the downlink signal DS (step S16). After that, the processing circuit 20 determines whether the transmission of the downlink signal DS has been completed. If it determines that it has not been completed, it returns to step S15 and waits for the next transmission timing (the time slot mentioned above) to arrive. On the other hand, if it determines that it has been completed, the processing circuit 20 returns to step S1 and waits for the start timing of the reception operation for the next uplink signal US.

[0042] As described above, the position detection system 1 according to this embodiment has a longer preamble section compared to a conventional uplink signal US having only two preambles PRE1, and it is possible to provide an uplink signal US that can be received by older pens that do not support the new protocol. Therefore, backward compatibility is ensured, and the occurrence of false detection of the uplink signal US due to noise is suppressed.

[0043] Further, according to the position detection system 1 of the present embodiment, the preamble PRE2 is configured to have a time-symmetric configuration with the preamble PRE1, so the time symmetry can be confirmed in steps S8 and S9 of FIG. 4. This allows the correctness of the preambles PRE1 and PRE2 to be confirmed from a perspective different from correlation detection. Therefore, according to the position detection system 1 of the present embodiment, it is possible to more effectively suppress the occurrence of false detection of the uplink signal US.

[0044] FIGS. 6(a) to 6(d) are diagrams respectively showing the configuration of an uplink signal US according to first to fourth modified examples of the present embodiment. Hereinafter, these modified examples will be described one by one in order.

[0045] First, referring to FIG. 6(a), in the uplink signal US according to the first modified example, the chip length of the preamble PRE2 (the number of chips constituting one preamble) is shorter than that of the preamble PRE1, and as a result, the time length of the preamble PRE2 is shorter than that of the preamble PRE1. Further, the preamble PRE2 according to the present modified example is configured by an autocorrelation code having a time-symmetric configuration with a part of the preamble PRE1. In this case, in step S8 of FIG. 4, the processing circuit 20 only needs to confirm the time symmetry using only that part of the preamble PRE1. Compared with the present embodiment, the present modified example has a shorter preamble part, so the effect of suppressing the occurrence of false detection of the uplink signal US is lower, but the present modified example can also obtain the same effect as the present embodiment.

[0046] Next, referring to Figure 6(b), in the uplink signal US according to the second modification, the chip length of the preamble PRE2 is longer than that of the preamble PRE1, and as a result, the time length of the preamble PRE2 is longer than that of the preamble PRE1. Furthermore, the preamble PRE2 in this modification is composed of an autocorrelation code having a portion that is time-symmetric with respect to the preamble PRE1. In this case, in step S8 of Figure 4, the processing circuit 20 only needs to use that portion of the preamble PRE2 to confirm the time symmetry. Comparing this modification to the embodiment, although the longer preamble portion puts pressure on the communication bandwidth, it is possible to suppress the occurrence of false detection of the uplink signal US more effectively than in the embodiment.

[0047] Here, in the first and second modifications, examples were described in which the chip length of preamble PRE2 differs from that of preamble PRE1. However, the chip rate (number of chips transmitted per second) of preamble PRE2 may also differ from that of preamble PRE1. If the chip rate of preamble PRE2 is higher than that of preamble PRE1, the time length of preamble PRE2 will be shorter than that of preamble PRE1, as shown in Figure 6(a). If the chip rate of preamble PRE2 is lower than that of preamble PRE1, the time length of preamble PRE2 will be longer than that of preamble PRE1, as shown in Figure 6(b). Since the way noise manifests may differ depending on the chip rate, configuring preamble PRE2 and preamble PRE1 so that their chip rates are different from each other makes it possible to suppress the occurrence of uplink signal US false detection more effectively than in this embodiment.

[0048] Furthermore, if the chip rates of preamble PRE1 and preamble PRE2 are different, the correlator for detecting preamble PRE1 and the correlator for detecting preamble PRE2 will calculate the correlation value at different periods corresponding to their respective chip rates. In this case, the processing circuit 20 should execute the determination process shown in step S3 of Figure 4 each time the calculation of the correlation value by either correlator is completed.

[0049] Next, referring to FIG. 6(c), the uplink signal US according to the third modification is configured to include two preambles PRE2. Each preamble PRE2 is arranged side by side before the first preamble PRE1. As described above, a plurality of preambles PRE2 may be arranged in the uplink signal US, and this also makes it possible to suppress the occurrence of false detection of the uplink signal US. Note that the code sequences constituting each preamble PRE2 may be the same or different from each other.

[0050] Next, referring to FIG. 6(d), the uplink signal US according to the fourth modification is configured to have, between the preamble PRE2 and the preamble PRE1, a blank period BR of a predetermined length of time during which the touch controller 31 does not perform carrier wave transmission. According to this modification, the same effects as those of the present embodiment can also be obtained.

[0051] FIGS. 7(a) and 7(b) are diagrams showing the configuration of an uplink signal US used in a fifth modification of the present embodiment. In this modification, two types of uplink signals US1 and US2 having different preamble part configurations from each other are used. The uplink signal US1 is the uplink signal US itself according to the background art of the present invention, and has a structure in which two preambles PRE1 and a data part are arranged in this order.

[0052] On the other hand, the uplink signal US2 has a structure in which the preamble PRE2 and the data section are arranged in this order with a blank period BR in between. The content of the data section of the uplink signal US2 is the same as the content of the data section of the uplink signal US1. The blank period BR has the same duration as the preamble PRE1, and when the touch controller 31 transmits uplink signals US1 and US2 simultaneously in a manner that will be explained later with reference to Figure 8, it synchronizes the transmission of the two uplink signals US1 and US2 so that the blank period BR of the uplink signal US2 occurs while the second preamble PRE1 of the uplink signal US1 is being transmitted. In this way, the pen 2 is able to receive the second preamble PRE1 of the uplink signal US1 without being disturbed by the uplink signal US2.

[0053] Since the preamble PRE2 of the uplink signal US2 is placed before the blank period BR, when uplink signals US1 and US2 are transmitted simultaneously, the first preamble PRE1 of uplink signal US1 and the preamble PRE2 of uplink signal US2 are transmitted simultaneously. Therefore, in this modified example, in order to enable separate reception of preambles PRE1 and PRE2 by pen 2, it is necessary to construct preambles PRE1 and PRE2 using mutually orthogonal autocorrelation codes. Note that any mutually orthogonal autocorrelation codes may be used as preamble PRE2, as shown in Figures 6(a) and 6(b). As an example, Figure 7(b) shows an example in which the autocorrelation code shown in Figure 6(b) (an autocorrelation code with a longer time duration than preamble PRE1) is used as preamble PRE2.

[0054] Figures 8(a) and 8(b) show methods for simultaneously transmitting two types of uplink signals, US1 and US2. In the method shown in Figure 8(a), the touch controller 31 transmits the uplink signal US1 from multiple Y electrodes 30Y and the uplink signal US2 from multiple X electrodes 30X. Of course, the touch controller 31 may also be configured to transmit the uplink signal US2 from multiple Y electrodes 30Y and the uplink signal US1 from multiple X electrodes 30X. In the method shown in Figure 8(b), the touch controller 31 uses every other Y electrode 30Y for transmitting the uplink signals US1 and US2. Of course, the touch controller 31 may also be configured to use every other X electrode 30X for transmitting the uplink signals US1 and US2.

[0055] The touch controller 31 can simultaneously transmit uplink signals US1 and US2 using either the method shown in Figure 8(a) or Figure 8(b). Alternatively, by utilizing the fact that preamble PRE1 and preamble PRE2 are orthogonal, it is also possible to configure the touch controller 31 to generate a signal consisting of the superimposed uplink signals US1 and US2 and transmit it from the same sensor electrode.

[0056] Although preferred embodiments of the present invention have been described above, the present invention is not limited in any way to these embodiments, and it goes without saying that the present invention can be implemented in various forms without departing from its essence.

[0057] For example, in the above embodiment, an example was described in which a code sequence obtained by converting a word into a chip sequence and then Manchester coding is used as preamble PRE1, and a code sequence obtained by time-reversing preamble PRE1 is used as preamble PRE2. However, preambles PRE1 and PRE2 are not limited to code sequences generated in this way. For example, a code sequence representing a word, or a code sequence representing a chip sequence obtained by converting a word, may be used as preamble PRE1 as is (i.e., without Manchester coding). Alternatively, a code sequence obtained by Manchester coding a word directly (i.e., without converting it into a chip sequence) may be used as preamble PRE1. Furthermore, instead of time-reversing preamble PRE1, which is a code sequence obtained by Manchester coding a word or a chip sequence, preamble PRE2 may be generated by time-reversing the word or a chip sequence. In this case, it is preferable to configure the touch controller 31 to transmit preambles PRE1 and PRE2 after Manchester coding them, and to configure the processing circuit of the pen 2 to verify the time symmetry between preamble PRE1 and preamble PRE2 after decoding the Manchester codes.

[0058] 1 Position detection system 2 Pen 3 Position detection device 3a Touch surface 20 Processing circuit 21 Battery 22 Core 23 Pen tip electrode 24 Pressure sensor 30 Touch sensor 30X X electrode 30Y Y electrode 31 Touch controller 32 Host processor BR Blank period DATA Data DS Downlink signal PRE1, PRE2 Preamble US, US1, US2 Uplink signal

Claims

1. A touch controller for transmitting an uplink signal having a structure in which a data section is arranged after a preamble section, wherein the preamble section includes a first preamble corresponding to a first protocol and a second preamble corresponding to a second protocol different from the first protocol, the data section has a format common to the first protocol and the second protocol, and the second preamble is arranged before the first preamble.

2. The touch controller according to claim 1, wherein at least a portion of the second preamble has a time-symmetric configuration with at least a portion of the first preamble.

3. The touch controller according to claim 2, wherein the second preamble is composed of a second code sequence obtained by reversing the time sequence of the first code sequence that constitutes the first preamble.

4. The touch controller according to claim 3, wherein the first code sequence is a Manchester-encoded code sequence.

5. The touch controller according to claim 3, wherein the first code sequence is a code sequence representing a word, or a code sequence obtained by converting the word into a chip sequence consisting of a predetermined number of chips.

6. The touch controller according to claim 5, which transmits a code sequence obtained by Manchester coding the first code sequence and the second code sequence.

7. The touch controller according to claim 1, wherein the second preamble is composed of a different sequence of codes than the first preamble.

8. The touch controller according to claim 7, wherein the second preamble is composed of a second code sequence having a different time length from the first code sequence that constitutes the first preamble.

9. The touch controller according to claim 8, wherein the chip length of the second code sequence is shorter than the chip length of the first code sequence, and the second code sequence has a time-symmetric configuration with respect to a portion of the first code sequence.

10. The touch controller according to claim 8, wherein the chip length of the second code sequence is longer than the chip length of the first code sequence, and the second code sequence has a portion that is time-symmetric with respect to the first code sequence.

11. The touch controller according to claim 8, wherein the chip rate of the second code sequence is different from the chip rate of the first code sequence.

12. The touch controller according to claim 1, wherein the preamble section has a plurality of second preambles.

13. The touch controller according to claim 12, wherein the plurality of second preambles are composed of the same code sequence.

14. The touch controller according to claim 13, wherein the plurality of second preambles are composed of different code sequences.

15. The touch controller according to claim 1, wherein the preamble section has a blank period between the second preamble and the first preamble during which no carrier wave is transmitted.

16. A pen for receiving an uplink signal having a structure in which a data section is arranged after a preamble section, wherein the pen receives the preamble section by detecting a structure in which a second preamble corresponding to a second protocol and a first preamble corresponding to a first protocol different from the second protocol are arranged in this order, determines a transmission and reception schedule based on the reception timing of the preamble section, and receives the data section and the preamble section of the next uplink signal according to the determined transmission and reception schedule.

17. The pen according to claim 16, wherein at least a portion of the second preamble has a time-symmetric configuration with at least a portion of the first preamble, and a correlation value calculation process using the code sequence constituting the second preamble and a correlation value calculation process using the code sequence constituting the first preamble are performed in parallel to detect a structure in which the second preamble and the first preamble are arranged in this order, and it is determined whether or not there is time symmetry between the detected at least a portion of the second preamble and the detected at least a portion of the first preamble, and the preamble portion is received in accordance with the determination that there is time symmetry.

18. The pen according to claim 17, wherein the preamble portion is transmitted in a Manchester coded state, and after decoding the Manchester code constituting the preamble portion, a determination is made as to whether or not there is time symmetry.

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